Salmonella is worse than we thought

Salmonella is not only surprising for tomato lovers, but also for scientists studying cone bacteria that cause suffering for millions of people.

In a study published June 4 in the online journal PloS One, researchers said they had discovered a molecular trick that could partly explain the ferocious nature of bacteria. The team from Rochester University Medical Center has identified a protein that allows bacteria to function quietly in the body. This gives them the time needed to gain a certain position in the organism before the resistance system is alerted to the intruder.

Dr. Jun Sun, the lead researcher and professor of gastroenterology and liver science, said: 'The immune system is alerted immediately after bacteria such as Salmonella appear, helping the body fight them quickly. . But Salmonella could be equipped with tools to allow them to hide from the early-stage resistance system. They develop quietly and make the host body weak. Salmonella is more insidious than we thought. '

Sun's team found that a toxic protein called AvrA is capable of weakening an alarm response . This helps the bacteria avoid the rage of the resistance system, which means giving them the time needed to develop before using energy to fight antibacterial cells such as neutrophil. These cells will attack the intruder very quickly if the bacteria use a more radiant method.

Salmonella.(Photo: picturethis.pnl.gov)

Sun said: 'AvrA helps Salmonella live peacefully with you, giving a little more time for them to survive in the body. That's bad news, because then the bacteria will spread. AvrA allows bacteria to harm the body without being detected. Bacteria have evolved for millions of years, they have learned some tricks that we may not understand. '

AvrA is one of the proteins in Salmonella that affects cells in the intestinal wall and the stomach is called epithelial cells. These cells are tightly linked by molecules called tightly bound proteins. These proteins form a sophisticated barrier to keep molecules or substances in the colon. Bacteria use some proteins that allow them to loosen these links, thereby breaking the barrier and preventing the body from being protected from infection.

While some Salmonella proteins allow it to loosen and drill through the protective barrier, Sun's team unexpectedly found that AvrA also helps the bacterium maintain those tight bonds . This ability reduces the body's alarm response while allowing bacteria to avoid detection of the immune system for a while, thus helping them to survive in the body. Severe symptoms of infection include vomiting, diarrhea, and abdominal cramps that occur anytime 8 to 72 hours after infection.

Sun, his team explored this phenomenon in cultured mice and human cells in the laboratory, saying: 'This is a surprising finding, that's why we Repeatedly repeat your research and perform multiple tests with different experimental methods. '

AvrA is one of the toxic proteins that Salmonella can optionally use, which uses a molecular mechanism such as a syringe to pump toxins and proteins into cells just seconds after it meets the first cell in the small intestine. and colon. This protein works very well at low acidity levels like the gut, which is very similar to another toxic protein called YopJ in Yersinia - the bacterium that causes Black Plague.

Sun is one of the scientists who has shown that AvrA reduces inflammation in the body. To some extent, it acts like a new arthritis cure by reducing the activity of inflammatory molecules called NF-Kappa B.

There are thousands of types of bacteria. Sun studied Salmonella Typhimurium, one of the two most common types; This bacterium along with Salmonella enteritis causes more than half of Salmonella-related diseases in humans. The type of bacteria emerging in tomatoes is a much rarer form, Salmonella saintpaul. Sun said the AvrA gene is present in more than 80% of Salmonella types, including 'saintpaul'.